Has to be a troll headline because anyone who would link to an article about a telescope running out of helium cryogenic, knows enough about cooling properties that space would not cool the instruments.

Heat transfer has a radiation term, actually, convection dominates under most conditions in the region of temperature and pressure we live in, but for very high temperatures and low pressures radiation can be a significant or even dominant factor.

But yes, since optical instruments tend to run at room temperature or lower (and radiation scales with T^4) you're going to have to rely mostly on some form of evaporation-based cooling out in space where there's no ambient convection or conduction. A system capable of cooling based on EM emission alone would need a farkton of surface area, which would backfire if your device ever saw the sun.

Jim_Callahan:Old Man Winter: GAH THE HEAT HAS NO WHERE TO GO. SCIENCE FOOL!

Heat transfer has a radiation term, actually, convection dominates under most conditions in the region of temperature and pressure we live in, but for very high temperatures and low pressures radiation can be a significant or even dominant factor.

But yes, since optical instruments tend to run at room temperature or lower (and radiation scales with T^4) you're going to have to rely mostly on some form of evaporation-based cooling out in space where there's no ambient convection or conduction. A system capable of cooling based on EM emission alone would need a farkton of surface area, which would backfire if your device ever saw the sun.

Well, unless it was a solar-sail conerider it's always going to spend some time with a large area facing the sun. Having it repeatedly change angle during orbit seems tricky but I suppose it is done with other satellites./yeah, subby failed hard

Honest Bender:verbal_jizm: Heat is molecular kinetic energy, Dumbmitter. Not much to transfer that to in a near vacuum.

Why does it get cold at night, but hot during the day?

Radiative cooling. Little to do with temperature differentials and something which, though accelerated in a vacuum due to the lack kind of any greenhouse effect, is not efficient enough to make a difference for this telescope.

But that does not change the reality that its tank is empty. The telescope can't exactly travel to Jupiter, harvest more helium, purify it, and use it to recharge its tank. And no one currently has any manned spacecraft capable of traveling to the Earth-Moon L2 point and the probe is not designed to be refill in any event.

In other words, they knew when they built the observatory that it would have a lifespan limited by its supply of coolant.

Honest Bender:Well, if they're using cryonic gas to cool something, slapping a heatsink on it and exposing it to space probably wont be enough cooling.

Exposing it to space would actually provide unwanted heating, not cooling.

The temperature of deep space (cosmic microwave background radiation) is about 2.7K. The boiling helium on this spacecraft cooled the instruments to 1.7K, and additional cooling systems took some detectors down to 0.3K (section 2.1.1.2).

Ivo Shandor:Honest Bender: Well, if they're using cryonic gas to cool something, slapping a heatsink on it and exposing it to space probably wont be enough cooling.

Exposing it to space would actually provide unwanted heating, not cooling.

The temperature of deep space (cosmic microwave background radiation) is about 2.7K. The boiling helium on this spacecraft cooled the instruments to 1.7K, and additional cooling systems took some detectors down to 0.3K (section 2.1.1.2).

Honest Bender:Well, if they're using cryonic gas to cool something, slapping a heatsink on it and exposing it to space probably wont be enough cooling.

This -

What they are effectively doing is taking the incident energy - the heat that the telescope is exposed to as well as the heat of the components running, and trying to transport it away to a 'safe' location from which they can get rid of the energy by focusing the heat onto a component which will "shine" and release the energy as light.

rubi_con_man:Honest Bender: Well, if they're using cryonic gas to cool something, slapping a heatsink on it and exposing it to space probably wont be enough cooling.

This -

What they are effectively doing is taking the incident energy - the heat that the telescope is exposed to as well as the heat of the components running, and trying to transport it away to a 'safe' location from which they can get rid of the energy by focusing the heat onto a component which will "shine" and release the energy as light.

Sure, if you can get at it. Our reserves on this planet are actually running out as helium just flies off the planet if released in the atmosphere. Current estimates say we could be in trouble of running out around 2030. If we want more we are going to need to goto the moon or another planetary body.

kryptin420:Seamer: Isn't helium one of the most abundant elements out there?

Sure, if you can get at it. Our reserves on this planet are actually running out as helium just flies off the planet if released in the atmosphere. Current estimates say we could be in trouble of running out around 2030. If we want more we are going to need to goto the moon or another planetary body.

The basic principles of radiative cooling of electronic components and subassemblies in a satellite are discussed, and estimates are made of the lowest temperatures attainable in a satellite by completely passive means. It appears feasible to maintain some compartments within a satellite at temperatures of 250Â°K or lower, so an opportunity is presented for refrigerating components whose characteristics are enhanced at lower temperatures. And:http://www.tak2000.com/data/Satellite_TC.pdf (page 50 and onward discuss passive cooling)